The present invention relates to an optical disk apparatus and an information recording method for the same including a laser driver mounted thereon, the laser driver supplying power to a laser to record information on an optical disk.
In the recording of data on an optical disk by emitting a laser beam thereonto, the waveform of each laser pulse of the laser beam is appropriately controlled according to the length of a mark or a space recorded on the disk to thereby record the data with high precision. The laser pulse is controlled by adjusting a current (to be referred to as “laser driving current” hereinbelow) supplied from a laser driver to the laser.
The laser driver includes a pulse controller to set a laser pulse using a pulse signal according to record data, a power setting section to set laser power, and a laser driver to drive a laser according to the pulse setting and the power setting.
The more the recording speed of the optical disk is, the more the laser power required to record data on the optical disk is. It is possible to increase the laser power by supplying a larger current from the laser driver to the laser. The more the current from the laser driver to the laser is, the more the power consumed by the laser driver (particularly by the laser driving section) is. This increases a calorific value or calorific power of the laser driver. When the temperature of the laser driver becomes higher, the temperature also becomes higher in a pickup on which the laser driver is mounted as well as in the laser mounted on the pickup.
It has been known that the power consumed by the laser driver is a product between a laser driving current supplied from the laser driver to the laser and a voltage (to be referred to as “headroom voltage” hereinbelow) obtained by subtracting “laser driving voltage” supplied to the laser from “power source voltage” supplied to the laser driver (particularly the laser driving section).
Also, there has been known a phenomenon in which when the laser driver temperature rises, the laser driving voltage supplied from the laser driver lowers. This phenomenon leads to a problem. That is, when the laser driver temperature rises, the laser driving voltage lowers and the headroom voltage becomes higher. This increases power consumption of the laser driver, and the calorific value of the laser driver becomes greater. Resultantly, the laser driver temperature further rises. This leads to a vicious cycle of the rising of the laser driver temperature.
To solve this problem, JP-A-2002-158395 and JP-A-2002-260266 propose a method in which by controlling the power source voltage such that the headroom voltage is kept fixed, the power consumed by the laser driver is kept fixed.